A square is inscribed in a circle of radius 10 cm. What is the area of the square, in square cm?

The square's diagonal is the circle's diameter, 20 cm, and a square of diagonal $d$ has area $d^2/2=400/2=200$ sq cm. The trap 400 takes the diagonal 20 cm as the SIDE; 100 takes the radius 10 cm as the side; 314 is the area of the circle itself, π $x10^2$ with π ≈ 3.14, which answers about the wrong figure.